Currently, a basic mechanism of online charging is as follows: A charging trigger function (CTF) applies to an online charging system (OCS) to reserve a quota of a rating group (Rating Group). The OCS grants the quota, and the CTF manages the quota, uses the quota, and collects charging information, and reports the collected charging information to the charging system when detecting that a charging reporting condition (a trigger condition) is met.
In a 4G network, a policy and charging enforcement function (PCEF) located at a gateway is a CTF, and the PCEF determines a charging mode (online charging or offline charging), a counting method (a volume, duration, or the like), a rating group (Rating Group, referred to as a charging key in this application), a reporting granularity, and the like according to a charging policy delivered by a policy and charging rules function (PCRF). A charging granularity includes SERVICE_IDENTIFIER_LEVEL or RATING_GROUP_LEVEL. If the charging granularity is RATING_GROUP_LEVEL, the PCEF needs to report charging information for each rating group. If the charging granularity is SERVICE_IDENTIFIER_LEVEL, the PCEF needs to report charging information for each rating group and each service identifier.
With a dramatic increase in a data volume, a new challenge is posed for a mobile network. To cope with the challenge, a mobile data network architecture in which a control plane and a user plane are separated is evolved. In this architecture, only control is performed on control planes, and the control planes may be deployed in a centralized manner; data flows pass through user planes, and the user planes are deployed in a distributed manner. A user may access a user plane nearby, to shorten a data transmission distance in a network, reduce a network delay, and improve network efficiency.
Currently, a network architecture in which a control plane and a user plane are separated has been extended in the 4G network, to implement, to some extent, charging in the network architecture in which the control plane and the user plane are separated. As shown in FIG. 1, a serving gateway-C, a PDN gateway-C, and a TDF-C are control planes, and a serving gateway-U, a PDN gateway-U, and a TDF-U are user planes. Generally, a control plane is a charging trigger point and performs a charging trigger function, and a user plane is a charging collection point and performs a charging collection function. In this architecture, a quantity of control planes and a quantity of user planes in a running state are in a ratio of 1:1.
However, with a dramatic increase in a mobile volume, a dramatic increase in a quantity of access devices, and enhanced requirements of a service on bandwidth, a delay, and the like, a relatively complex network architecture facing a future service requirement is evolved. For example, with movement of a user, pressure on a user plane, and a special requirement of a user service, user planes accessed by the user may be relatively frequently switched. Alternatively, a user may have a plurality of user planes at the same time, and a service data flow of the user is migrated between different user planes. A current charging mechanism cannot implement accurate charging processing in such a scenario.